Chemistry/Storage/Stability/Compatibility
- A synthetic xanthine derivative structurally related to caffeine and
theophylline, pentoxifylline occurs as a white, odorless, bitter-tast­ing,
crystalline powder. At room temperature, approximately 77 mg are soluble
in one ml of water and 63 mg in one ml of alcohol.The commercially
available tablets should be stored in well-closed containers, protected
from light and at 15-30°C. Pentoxifylline is also known as oxpentifylline
or BL-191.

Uses/Indications
- In
horses, pentoxifylline has been used as adjunctive therapy for
endo­toxemia and in the treatment of navicular disease. At the time of
writing, the drug is still under investigation to document both safety and
efficacy for these purposes.

Pentoxifylline has
been used in dogs to enhance healing and reduce inflammation caused by
ulcerative dermatosis in Shelties and Collies and for other conditions
where improved microcirculation may be of benefit.

Pentoxifylline’s major
indications for humans include symptomatic treatment of periph­eral
vascular disease (e.g., intermittent claudication, sickle cell disease,
Raynaud’s, etc.) and cerebrovascular diseases where blood flow may be
impaired in the microvasculature.

Pharmacokinetics
- A pharmacokinetic study done in horses showed high interpatient
variability in absorption of oral dosage forms with peak levels occurring
1 - 10 hours after oral dosing. No significant difference in relative
bioavailability was noted between whole and crushed extended-release
tablets. The drug appears to rapidly eliminated (half life of about one
hour after IV dosing). Because of the wide interpatient variability, the
authors were unable to make dosing recommendations for clinical use.

In humans,
pentoxifylline absorption from the gastrointestinal tract is rapid and
almost complete, but a significant first-pass effect occurs. Food affects
the rate, but not the extent of absorption. While the distributive
characteristics have not been fully described, it is known that the drug
enters maternal milk. Pentoxifylline is metabolized both in the liver and
in erythrocytes and all identified metabolites appear to be active.

Contraindications/Precautions/Reproductive Safety
- Pentoxifylline should be consid­ered contraindicated in patients who
have been intolerant to the drug or xanthines (e.g., theophylline,
caffeine, theobromine) in the past and those with cerebral hemorrhage or
retinal hemorrhage. It should be used cautiously in patients with severe
hepatic or renal impairment and those at risk for hemorrhage.

Although safety in
pregnant, lactating or breeding animals has not been established, stud­ies
in pregnant rats and rabbits demonstrated no overt teratogenicity. As
pentoxifylline and its metabolites enter maternal milk, benefits to the
mother should be weighed against the risks to offspring.

Adverse
Effects/Warnings
- Most commonly reported adverse effects involve the GI tract (vomiting/inappetence).
There are reports of dizziness and headache occurring in a small
percentage of humans receiving the drug. Other adverse effects, primarily
GI, CNS and cardiovascular related have been reported in people, but are
considered to occur rarely. Note: Veterinary experience is limited with
pentoxifylline and animal adverse ef­fects may differ.

Drug Interactions
- Use of non-steroidal antiinflammatory agents with pentoxifylline in
horses is controversial. Some sources state that when used for endotoxemia
in horses, pen­toxyfilline’s beneficial effects are negated by NSAIDs,
but one study showed superior ef­ficacy when flunixin and pentoxifylline
were used together compared with either used alone. Ciprofloxacin
(other quinolones too?) and cimetidine can increase pentoxifylline
serum levels. Increased adverse effects of pentoxifylline may result. When
pentoxifylline is used with warfarin or other anticoagulants,
increased risk of bleeding may result. Use together with enhanced
monitoring and caution. Theophylline blood levels may be increased
when used concurrently with pentoxifylline.

b) For treatment of
navicular disease: 6 grams per day PO for 6 weeks (Livesay 1996)

Monitoring
Parameters
- Efficacy and adverse effects

Client Information
- To reduce the GI effects of pentoxifylline, give with food. Clients
should understand that veterinary experience with this medication is
limited and that the risk versus benefit profile is not well defined.

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